Acumulação de metais pesados e alteração das propriedades físicas e químicas de areias de dunas litorâneas

Abstract

During past two centuries, dunes Portuguese coastline is being used for agricultural practices with intensive use of agrochemicals and deficient technical inspection. These uses have been changing the texture and the physical and chemical composition of the sands with increased effects on the heavy metals accumulation. In order to evaluate the changes, samples of dunes, with and without agricultural uses, were collected and analyzed the chemical and physical parameters. Sieve shakers were used to determine the granulometry and the fine fraction (particles sizes with a diameter less than 0.074 mm); MAB-Peroxide method was used to evaluate the organic matter content. Following electrochemical method it was measured humidity, pH, electrical conductivity and oxidation-reduction. Mineral composition was analyzed by Portable X Ray fluorescence. This study shows an increase trend from natural dune to the agricultural land in the fine particles sizes, organic matter content, humidity, electrical conductivity and oxidation-reduction; pH decreased from basic conditions to an approximately neutral value, thus increasing the risk of metals mobility. A general accumulation of metals in the sand dunes with a special increase in the total concentration of Fe, Mn, Cu, Zn, Pb, As, Zr, Th, Rb, Cr, V, Ni, Hg, Co and U was detected.